1866.] GODWIN- AtrSTEN BELGIAN TERTIAEIES. 241 



North Atlantic, both Eastern and Western, and the Southern or 

 Lnsitanian. 



The greater extent of circumpolar land would exercise a great 

 influence on the course of the North Atlantic Ocean-current, and the 

 general temperature of its waters,froni 55° to 65° N. lat., would have 

 been much higher than at present. Under these conditions there 

 would have been an extension eastward of the transatlantic littoral 

 fauna, whilst at the same time the temperature would encourage a 

 more northern range of Lusitanian forms. 



The marine beds of the Tagus, of the Adour, of the Loire, and of 

 the English Channel, which were indents from the Eastern Atlantic, 

 have this common characteristic, that the fauna of each, so far as 

 living species can guide us, is more southern than that of the corre- 

 sponding coast at present ; and this order of diiference is progressive 

 from south northwards, so that whilst the beds of the English Channel 

 have Lusitanian relations, those of Touraine, and to a greater extent 

 those of Bordeaux* and the places south connect themselves with the 

 West African marine fauna. 



2. Zoological Features. — The Crag fauna of the EngHsh area is in- 

 complete, so also is that of Belgium ; taken together, thej form a 

 completer marine fauna, representing a greater range of sea-zones. 



Various comparisons have been made for percentage calculations 

 between the shells of the " Crag jaune" and the " Crag gris," and 

 again between those from the Scaldesien generally and the " Crag 

 noir " or Diestien. 



It will not be necessary here to reproduce the whole of M. Nyst's 

 latest lists, given in the work of Omalius ; for the first comparison 

 the differences in the first two lists will sufiice. It might be ex- 

 pected, from the extent to which the Diestien beds have been denuded, 

 that the whole of their proper fauna should be met with in the 

 Scaldesien beds which resulted from that change ; it is so to a great 

 extent, but it is also evident on the spot that it is mainly the stronger 

 shells which have endured removal ; besides this, in the Antwerp 

 district, where alone true Scaldesien beds occur, the Diestien beds on 

 which they lie have not been denuded quite so low as the second 

 life-zone (Edeghem, Fort Herenthal), in which the deepest water 

 assemblage is met with. 



It would appear, so far as collections at present indicate, that of 

 143 species enumerated by M. Nyst, there are some in the " Crag 

 jaune " which are scarce or wanting in the " Crag gris" (Tab. I.), 

 and in the latter, some wanting in the other (Tab. II.) ; but the lists 

 may be somewhat reduced by removing such species as are known 

 only as Belgic at present. Paludestrina'? terehellata, N. ; Turhinella 

 internodula, N. ; Eulima Icevis, 'N. ; Natica proxima (a doubtful 

 species) ; Cancellaria minuta, N. (un seul individu) ; Pleurotoma 

 turrifera ? P. costata ; P. histrix ; P. Woodii ; Murew tortuosus, M. C. 



* The boundary of the Crag sea is so traced on its eastern side as to include 

 the Upper Kainozoic formations near Cassel, Luithorst, Freden, and Dichholtz ; 

 these are all in the latitude of the Belgian crag, and along the courses of the 

 Weser and Lesse. 



